The melt crystallisation of PEEK has been analysed using dynamic small and wide angle scattering, in addition, differential scanning calorimetry has also been used. The crystallisation data have been analysed in terms of the Avrami, Hoffman-Lauritzen and Cahn-Hilliard models. The mechanistic n values, nucleation constant, K-g, and the effective diffusion co-efficient for the crystallisation of PEEK in the temperature range 290-320 degreesC are reported. These results are discussed in terms of the level of insight they give into the nucleation process. (C) 2003 Elsevier Ltd. All rights reserved.